1. Technical Field
The present invention relates to semiconductor process methods, and more particularly, to methods for thermal process in packaging assembly of semiconductor.
2. Description of the Related Art
Most of thermal processes in current semiconductor packaging assembly are to transfer the heat by conduction (hot plate), convection (gas or fluid) or radiation (infrared, laser, microwave or lamps). The curing, soldering reflow, thermal bonding and RTP (rapid thermal process) are now used in semiconductor manufacturing process.
Reference is now made to FIG. 3, which illustrates that a semiconductor work 121 includes heterogeneous chip combination (thin silicon chip 131, thick silicon chip 137 and stacked silicon chips 133) and substrate 135 (such as silicon wafer or organic substrate). FIG. 3-1 illustrates tiny metal joints 147 between the thin silicon chip 131 and substrate 135. The tiny metal joint 147 is composed of a copper post 141 of the thin silicon chip 131, solders or intermediate metal layers 143, and a copper pad 145 of the substrate 135.
Reference is now made to FIGS. 4 and 4-1, which illustrate one occasion of conventional radiation heating process, such as RTP (rapid thermal process). The IR lamp 151 generates radiation light and transfers heat onto the surface of chips 131, 133, 137 and substrate 135 through radiation light itself. Meanwhile the heat on the surface of the chips 131, 133, 137 and the substrate 135 is transferred into inner structures of the chips 131, 133, 137 and the substrate 135 by conduction. However, the radiation light cannot transit chips directly and the shadow area that the radiation light cannot reach does not receive the heat from radiation light.
Reference is now made to FIGS. 5 and 5-1, which illustrate one occasion of convection heating process, such as hot air heating process. The gas blower 161 generates heated airflows and transfers heat onto the surface of the chips 131, 133, 137 and the substrate 135 through airflows. Meanwhile the heat on the surface of the chips 131, 133, 137 and the substrate 135 is transferred into internal structures of the chips 131, 133, 137 and the substrate 135 by conduction. However, the airflow distribution depends on the shape and structure of chips.
Reference is now made to FIG. 6, which illustrates one occasion of conduction heating process, such as hot plate heating process. The hot plate heater 173 is composed of a hotplate in which electrodes 171 are placed. The hot plate heater 173 generates heat from the electrodes 171 and transfers the heat to the chips 131, 133, 137 and the substrate 135 by conduction. However, uneven contact surface will cause the heat transfer to the substrate 135 less equal.
The heat transfer processes which apply to the semiconductor work 121 by the above conventional heat transfer methods have the following phenomena: higher peak temperature, much more variations in temperature distribution and not easy control of temperature profile due to the warpage and the mismatch of coefficient of thermal expansion (CTE) between the substrate 135 and heterogeneous chip combination (thin silicon chip 131, thick silicon chip 137 and stacking silicon chips 133) during the thermal process. Therefore, the above conventional heat transfer methods to the semiconductor work 121 have the bad production yield during packaging assembly of semiconductor and the poor performance of chips consequently.
Accordingly, there exists a need to provide a solution to solve the aforesaid problems.